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Running a law firm means your income rarely arrives on a predictable schedule. A large settlement lands in March. A retainer clears in July. A slow fourth quarter follows a busy third. That irregularity makes estimated tax payments one of the most common financial blind spots for attorneys who own their practice — and the mistakes compound quietly until they show up as an unpleasant surprise or a penalty notice from the IRS.
Unlike W-2 employees, partners and solo practitioners don't have taxes withheld from every paycheck. You're responsible for paying as you earn, in four installments, based on your own projection of income. Get that projection wrong and you either overpay and starve your firm of cash, or underpay and face penalties plus a scramble to cover the shortfall.
Nearly every mistake below is a version of the same error: estimating from the rearview mirror — calculating this quarter's payment from last year's return, last quarter's habits, or a bank balance that reflects the past rather than a current projection of where this year is actually heading. Solid bookkeeping for attorneys is what makes forward-looking estimates possible: when your books are current, quarterly payments become a calculation. When they lag, every deadline turns into a fire drill.
Here are the mistakes we see most often, and what to do instead.
The simplest way to calculate estimated payments is to base them on last year's tax liability, divided into four equal installments. The IRS even provides a safe harbor for this approach under its estimated tax rules for individuals, which can protect you from underpayment penalties even if your actual liability this year is higher.
The mistake is treating that safe harbor as a substitute for planning rather than a floor. If your firm added a partner, closed a major case, or shifted from contingency work to hourly billing, last year's numbers no longer reflect your trajectory. Attorneys who rely solely on the safe harbor often end up owing a large balance at filing time — the safe harbor prevents a penalty, but it does nothing to prevent the bill itself. If your income is climbing, project current-year income and adjust payments upward so April doesn't become a cash crisis.
Key Takeaway: The safe harbor is penalty protection, not tax planning. In a growth year, the gap between safe-harbor payments and your actual liability becomes an interest-free loan you're taking from yourself — one that comes due all at once at filing time. Budget for the real number, not the protected one.
This is the mistake that catches the most attorneys off guard, particularly those running their practice on a cash basis. A large settlement or retainer deposit inflates your bank balance, but not all of it is profit — and not all of it is even yours yet if a portion belongs to a client trust obligation. Firms that mix operating cash with tax reserves tend to spend today what should have been set aside for the next estimated payment.
The fix is structural, not behavioral. Open a separate account and move a fixed percentage of every deposit into it as income arrives, before you touch it for overhead or owner draws. This single habit does more to prevent estimated tax shortfalls than any amount of discipline applied at quarter-end. It also gives you something useful in return: a real-time view of your true, after-tax profitability rather than an inflated cash balance that disappears when tax season arrives. Our guide on cash versus accrual accounting for law firms walks through how your accounting method affects when income actually counts for tax purposes — which directly shapes how much you should be setting aside.
Key Takeaway: Your bank balance is a lagging indicator; your tax reserve account is a leading one. Once a fixed percentage of every deposit moves automatically, the reserve balance itself becomes a planning tool — if it looks light relative to year-to-date profit, that's your earliest warning that your projection has drifted from reality.
How your firm is structured determines who owes the estimated tax and how it flows through. Solo practitioners and single-member LLCs generally handle this at the individual level. Partnerships pass income through to partners via K-1s, and each partner is individually responsible for estimating and paying tax on their share — regardless of whether that income was actually distributed in cash. S corporation shareholders who take a salary have withholding on the wage portion but still owe estimates on any pass-through profit above that salary.
Attorneys who recently changed structure — converting from a partnership to an S corporation, or adding a partner — are especially prone to miscalculating, because the mechanics shifted and their habits did not. If you're unsure how your current entity affects your estimated tax obligations, our comparison of S corp versus partnership structures for law firms is a useful starting point, and it's worth revisiting anytime your ownership structure changes.
Estimated payments are due four times a year, but the mistake happens well before each deadline: many attorneys don't look at their year-to-date profit and loss until the payment is already due, which leaves no time to adjust withholding, defer income, or accelerate deductible expenses. By the time you're calculating the payment, most of your planning options for that quarter have already closed.
A better rhythm treats each quarter as a checkpoint, not just a payment deadline. Before each due date, review:
This quarterly check-in is also the right moment to revisit retirement plan funding, which remains one of the most effective ways for profitable firm owners to reduce current-year taxable income while building long-term savings — a topic we cover in depth in The Three Buckets of Retirement Planning for Law Firm Partners.
In multi-partner firms, estimated tax mistakes often happen not at the firm level but at the individual partner level. Each partner may have different outside income, different filing status, different state residency, and different withholding from other sources. A single firm-wide estimate that ignores these differences will be wrong for at least some partners — and often for all of them.
Partners who moved between states, added a working spouse's income, or took on outside board or consulting work need their own projection, not a share of a generic firm number. This is particularly relevant for firms with partners split between New York and other jurisdictions, where state estimated tax rules and due dates don't always mirror federal deadlines. Our article on year-end planning for law firm partners addresses several of these individual variables in more detail.
Key Takeaway: As your firm grows, estimated tax planning shifts from one calculation to many. A firm-wide estimate that worked at two partners breaks at five — the right cadence is a firm-level projection each quarter, translated into a partner-level number for anyone whose circumstances changed since last year.
Estimated tax mistakes rarely stem from a single bad decision. They accumulate from books that lag reality, shortcuts that substitute last year's numbers for this year's, and skipped quarterly check-ins that would otherwise catch an income shift before it becomes a liability. The firms that handle this well have one thing in common: bookkeeping that is current, accurate, and reviewed regularly by someone who understands how law firm income actually moves.
That's the system Revonary builds for the law firms we work with — current books, a quarterly projection rhythm, and partner-level estimates that reflect each owner's actual situation. If your quarterly payments still feel like guesswork, schedule a conversation with Revonary and let's replace the rearview-mirror estimate with a forward-looking one.